/*
  将下面异步代码使用 Promise 的方法改进
  尽量用看上去像同步代码的方式
  setTimeout(function () {
    var a = 'hello'
    setTimeout(function () {
      var b = 'lagou'
      setTimeout(function () {
        var c = 'I ♥ U'
        console.log(a + b +c)
      }, 10)
    }, 10)
  }, 10)
*/


var a = new Promise(resolve=>{
  setTimeout(()=>{
    resolve('hello');
  })
})
var b = new Promise(resolve=>{
  setTimeout(()=>{
    resolve('lagou');
  })
})
var c = new Promise(resolve=>{
  setTimeout(()=>{
    var c = 'I ♥ U'

    resolve(c);
  })
})
Promise.all([a,b,c]).then((arr)=>{
  var a = arr.reduce((prev,next)=>{
    return prev + next;
  },'')
  console.log(a)
})


